Update Vaultwarden guide

[nmelehan-akamai]

An Akamai customer has reported that the Vaultwarden guide here is out of date and needs to be updated:
https://www.linode.com/docs/guides/how-to-self-host-the-vaultwarden-password-manager/

They were not specific about the errors they encountered. The guide also uses an old version of Ubuntu (20.04).

The guide should be updated to use Ubuntu 24.04, and to correct any technical errors that may exist.

[nmelehan-akamai]

Assigning to @DHBR2